OMG, what I've done?

Couple of days ago, I tried using macport to install something, because I'm using Xcode 4.3 and the command-line tool hadn't been installed by the time, macport wouldn't work. So I followed some guide to get command-line tool installed, then I used following command:

sudo xcode-select -switch /Applications/Xcode.app/ 

which I think screwed everything except macport: now, in Xcode, even a simple single-view iOS project won't be compiled, it says "UIKit/UIKit.h not found".

Does anyone know how to correct this? I don't want to re-install the gigantic Xcode again, gotta do some iOS project tonight, help!